(1) State of the Invention
The present invention describes a class of enhancer polymers used with light producing 1,2-dioxetanes to produce enhanced chemiluminescence. Enhancers are substances which increase the amount of chemiluminescence emitted by the 1,2-dioxetane. The enhancer polymer can act to increase the fluorescence quantum yield of the 1,2-dioxetane and can include a fluorescent energy acceptor compound which is excited by an excited species produced in the decomposition of the 1,2-dioxetane and then emits light. The enhancer can act to increase the percentage of 1,2-dioxetane molecules which produce an electronically excited state product and thus more light. For the purposes of this invention, enhanced chemiluminescence means that the total light emitted, the maximum light intensity and/or the ratio of light intensity of the reaction compared to the background is greater than that observed in the absence of the enhancer. A preferred 1,2-dioxetane reaction is as follows: ##STR1## wherein R.sub.1, R.sub.3 and R.sub.4 are various organic groups and R.sub.2 is an aryl group substituted with OX(X-oxy) group.
(2) Prior Art
1. Enhancers of Chemiluminescent Reactions not Involving Dioxetanes. Various substances are known including 4-substituted phenols, 6-hydroxybenzothiazole and its derivatives and several aromatic amines which enhance the chemiluminescent output from the oxidation of luminol by a peroxide in the presence of a peroxidase enzyme (European Patent No. 0087959; U.K. Patent Application GB 2162946A: T. P. Whitehead et al, Nature 158 (1983)). The nature of the enhancement is not well understood but is thought to be due to the enhancer substance acting as a redox mediator in the enzymatic reaction (L. J. Kricka, G. H. G. Thorpe and R. A. W. Stott, Pure and Appl. Chem., 59 (6), p. 651 (1987); G. H. G. Thorpe and L. J. Kricka, Bioluminescence and Chemiluminescence New Perspectives, John Wiley & Sons, Chichester, p. 199 (1987)). Enhancement is in any case, not thought to be due to an increase in the fluorescence quantum yield of the excited aminophthalate product nor due to energy transfer to a fluorescer nor to an increase in the yield of chemically produced excited states.
2. Enhancement by Surfactants of Chemiluminescence not involving Dioxetanes. Enhancement by surfactants of the chemiluminescent oxidation of luminol (K. D. Gundermann, Bioluminescence and Chemiluminescence, Academic Press, New York, p. 17 (1981); D. I. Metelitza, A. N. Eryomin and V. A. Shibaev, J. Biolumin. and Chemilumin., 7, 21 (1982)) has been reported. Chemiluminescence from the chemical oxidation of luciferin was found to increase in the presence of various surfactants due to an increase in the fluorescence quantum yield of the excited state product (T. Goto and H. Fukatsu, Tetrahedron Lett., 4299 (1969)). On the other hand, enzymatic oxidation of luciferin was found to increase in the presence of nonionic surfactants due to an increase in the turnover rate of the enzyme (L. J. Kricka and M. DeLuca, Arch. Biochem. Biophys., 217, 674 (1983)). Enhancement of the chemiluminescent oxidation of acridinium esters by a cationic surfactant was reported to be due to suppression of a competing non-chemiluminescent side reaction (F. McCapra, Acc. Chem. Res., 9, 201 (1976)). U.S. Pat. No. 4,927,769 to Chang discloses various enhancers.
3. Chemical Triggering of Dioxetanes. The first example in the literature is described in relation to the hydroxy-substituted dioxetane derived from the 2,3-diaryl-1,4-dioxene (A. P. Schaap and S. Gagnon, J. Amer. Chem. Soc., 104, 3504 (1982)). However, the hydroxy-substituted dioxetane and any other examples of the dioxetanes derived from the diaryl-1,4-dioxenes are relatively unstable having half-lives at 25.degree. C. of only a few hours. Further, these non-stabilized dioxetanes are destroyed by small quantities of amines (T. Wilson, Int. Rev. Sci.: Chem., Ser. Two, 9, 265 (1976)) and metal ions (T. Wilson, M. E. Landis, A. L. Baumstark, and P. D. Bartlett, J. Amer. Chem. Soc., 95, 4765 (1973); P. D. Barlett, A. L. Baumstark, and M. E. Landis, J. Amer. Chem. Soc., 96, 5557 (1974)), both components used in the aqueous buffers for biological assays.
Examples of the chemical triggering of stabilized dioxetanes were first reported in U.S. Pat. No. 4,857,652 to Schaap and a paper (A. P. Schaap, T. S. Chen, R S. Handley, R. DeSilva, and B. P. Giri, Tetrahedron Lett., 1155 (1987)). These dioxetanes exhibit thermal half-lives of years but can be triggered to produce efficient chemiluminescence on demand.
4. Enzymatic Triggering of Dioxetanes. The first examples of enzymatic triggering of dioxetanes are described in U.S. Pat. No. 4,857,652 to Schaap and a series of papers (A. P. Schaap, R. S. Handley, and B. P. Giri, Tetrahedron Lett., 935 (1987); A. P. Schaap, M.D. Sandison, and R. S. Handley, Tetrahedron Lett., 1159 (1987) and A. P. Schaap, Photochem. Photobiol., 47S, 50S (1988)). The highly stable adamantyl-substituted dioxetanes bearing a protected hydroxyaryl substituent are triggered to decompose with emission of light by the action of an enzyme which removes the protecting group. The hydroxyaryl group is subsequently converted at pH &gt;9 to a strongly electron-donating aryloxide anion which dramatically increases the rate of decomposition. As a result, chemiluminescence is emitted at intensities several orders of magnitude above that resulting from slow thermal decomposition. Bronstein PCT 88 00695 also describes enzyme triggerable dioxetanes as does Bronstein U.S. Pat. Nos. 4,948,614, 4,952,707, 5,032,381 and 4,931,223. It is anticipated that chemiluminescence from the triggerable dioxetanes described in these references can also be enhanced by the polymers of the present invention.
5. Fluorescent Enhancers Covalently Attached to Dioxetanes. Stable, triggerable dioxetanes with appended fluorescent groups are reported in U.S. Pat. No. 5,013,827 to Schaap. These compounds differ from the present invention in that enhancement of chemiluminescence occurs through a radiationless intramolecular energy transfer from the initially excited meta-oxybenzoate chromophore to a more highly fluorescent fluorophore.
6. Enhanced Chemiluminescence From Dioxetanes in the Presence of Surfactants. A chemiluminescent reaction believed to involve a non-isolable dioxetane was enhanced in micellar solution (S. Shinkai, Y. Ishikawa, O. Manabe and T. Kunitake, Chem. Lett., 1523 (1981)). The mechanism of enhancement remains unproven but the authors suggested that the yield of excited state products may be increased in the hydrophobic micellar environment as compared to water.
Schaap et al first reported the enhancement of chemiluminescence from the enzyme-triggered decomposition of a stable 1,2-dioxetane in the presence of water-soluble substances including an ammonium surfactant and a fluorescer. Fluorescent micelles consisting of cetyltrimethylammonium bromide (CTAB) and 5-(N-tetradecanoyl)aminofluorescein capture the intermediate hydroxy-substituted dioxetane and lead to a 400-fold increase in the chemiluminescence quantum yield. Enhancement occurs by virtue of an efficient intermolecular energy transfer process from the anionic form of the excited state ester to the fluorescein compound which is held in close proximity and the hydrophobic environment of the surfactant (A. P. Schaap, H. Akhavan and L. J. Romano, Clin. Chem., 35(9), 1863 (1989)). ##STR2##
U.S. Pat. Nos. 4,959,182 and 5,004,565 to Schaap describe additional examples of enhancement of chemiluminescence from chemical and enzymatic triggering of stable dioxetanes in the presence of the ammonium surfactant and fluorescers.
Fluorescent micelles formed from CTAB and either the fluorescein surfactant described above or 1-hexadecyl-6-hydroxybenzothiaxamide enhance the chemiluminescence from the base-triggered decomposition of hydroxy- and acetoxy-substituted dioxetanes. It was also reported that CTAB itself can enhance the chemiluminescence of dioxetane 1 (U.S. Pat. Nos. 4,959,182 and 5,004,565 to Schaap). The phosphate-protected dioxetane 1 (Lumigen.RTM. PPD) has proven commercially useful for the sensitive detection of alkaline phosphatase. Chemiluminescent detection using LumiPhos.RTM. 530, a ready-to-use liquid formulation containing, has been employed in Southern blotting (D. Pollard-Knight, A. C. Simmonds, A. P. Schaap, H. Akhavan, and M. A. W. Brady, Anal. Biochem., 185, 353 (1990)), a microtiter plate based DNA probe sandwich assay (J. M. Clyne, J. A. Running, R. Sanchez-Pescador, D. Besemer, M. Stempien, A. P. Schaap, R. S. Stephens, and M. S. Urdea, J. Biolumin. Chemilumin. 2, 193 (1988)) and Western blotting (R. Oberfelder, Focus, 13, 50 (1991); G. S. Sandhu, B. W. Eckloff, B. C. Kline, BioTechnques 11, 14 (1991)).
U.S. Pat. No. 4,978,614 to Bronstein and U.K. Patent Application No. 89/14749.0 (GB 2,233,451A) disclose enhancement of dioxetane chemiluminescence by polymeric quaternary ammonium compounds alone or admixed with fluorescein. Other substances reported to enhance chemiluminescence include globular proteins such as bovine albumin, quaternary ammonium surfactants, nitrogen-containing polymers and polyethers. No phosphonium polymers are disclosed.
7. Polymeric Phosphonium Salts. Polyvinylbenzyltrimethylphosphonium salts, polyvinylbenzyltriethylphosphonium salts and polyvinylbenzyltributylphosphonium salts have not been reported. Polyvinylbenzyltrihexylphosphonium salts are disclosed in a patent prepared as a copolymer with divinylbenzene (PCT Int. Appl. WO 8906380 A1 13 Jul. 1989). Polyvinylbenzyldiethylphenylphosphonium salts are disclosed in a patent prepared as a copolymer with styrene (Jpn. Kokai Tokkyo Koho, JP 63243964 A2 11 Oct. 1988). Polyvinylbenzyltrioctylphosphonium salts are disclosed in a series of patents (U.S. Pat. No. 4,338,095 A 6 Jul. 1982 and EPA 28,123 Eur. Pat. Appl. EP 8233 20 Feb. 1980, Eur. Pat. Appl. EP 28123 6 May 1981) as being useful for the fluorescent detection of bilirubin. Polyvinylbenzyltriphenylphosphonium salts are well known in the literature, being used as surfactants, phase-transfer catalysts and reagents in organic synthesis. Copolymers of Polyvinylbenzyltriphenylphosphonium salts with acrylic acid, butadiene and divinylbenzene are known. None of the foregoing polymers or copolymers have been used as enhancers of chemiluminescence of 1,2-dioxetanes. No reports of covalently linked fluorescers to these polymeric phosphonium salts have been made. No polyvinylbenzyltrialkylphosphonium salts with mixed pendant groups have been reported.